Three years later, an enormous iceberg detached near Antarctica's McMurdo Sound. According to Williams and her colleagues, the event was caused by global warming, which has likely been melting and weakening ice at the poles.

Fighting for air

"We started out with 3 feet (90 centimetres) of ice and were up to a 9 feet (2.7 metres) thickness" by 2002, the last year of the study, Williams says.

Filming both above and below the thickened ice, Williams and her colleagues observed seals lining up to breathe at the few holes they were able to make with their front canine teeth. Lacking the energy to swim further, fights ensued in the lines, with animals lashing out at each other for access to air.

Williams says that after B-15 dislodged, there were 130 kilometres of ice between McMurdo and the open ocean.

"Weddell seals can only swim 4 miles (6.4 kilometres) under ice before they have to come up to breathe, so you can see the problem," she says.

The researchers measured the oxygen consumption of seals that managed to surface, and by analysing the underwater video, calculated the energy cost of each stroke the seals made during dives.

After comparing these calculations with prior data on seals diving under normal conditions, the researchers found that the new environment simultaneously increased the seals' need for oxygen and reduced their access to air.

Since seals dive to hunt, most were unable to catch enough prey to sustain themselves and their pups.

"Perhaps the most difficult (to observe) were the abandoned pups. The first rule as a biologist is to let nature take its course, but is this truly nature when global warming due to human perturbation has instigated the event?" Williams said. "It was exceptionally difficult to walk away from crying pups, knowing that the ice conditions likely cause their mothers to leave."

A march too far

Seals weren't the only victims of the B-15 break-off.

As fans of the popular film 'March of the Penguins' know, the flightless birds must travel long distances to feed at sea before returning to their chicks.

After the drifting iceberg thickened the ice surrounding Ross Island, the researchers observed Adelie penguins struggling to complete a trek that is arduous even under normal conditions.

"With the ice edge so far away it was an impossible travel [a long] distance, so many made a one-way trip and abandoned their nests," Williams says, adding that other biologists in the region reported that many of the nests "failed."

Professor Hannah Carey, past president of the American Physiological Society and a professor of comparative biosciences at the University of Wisconsin School of Veterinary Medicine, says the new research is "compelling" and "may represent one of the best links we have between climate change and the physiology of individual animals, particularly for Antarctic vertebrates."

She says evidence has been mounting that climate-related effects have been disrupting hibernating animals, fish populations, amphibians and other groups, but little work has been done on the physiological impacts to individual animals, and the implications these have for survival of adults and their young.

Far-reaching impacts

Carey also says the new research demonstrates how a warming event at the poles can actually lead to ice thickening in other regions, illustrating how "climate change [impacts] on animals can be less predictable and more variable than we may have thought."

"In a period where global climate change is occurring, scientific studies that investigate the interactions of physiology, behaviour, ecology and the physical environment are needed now more than ever," he says.

"These types of studies will help us predict how environmental changes may influence animal populations and contribute to our making informed decisions about conservation efforts."

Both Hicks and Williams hope greater emphasis will be placed on animal physiology studies in the future, as a means of understanding how global environmental challenges can impact animals, including humans.

Williams, however, said the best preventive action "is to get people to recognise the domino effect of human impacts."

"Who could have imagined that driving a car in the US could result in a Weddell seal pup freezing to death in the Antarctic?" she says. "But it did."